An enhanced power control method for use in a wireless packet-switched network having an interference prediction algorithm which includes an error margin. In particular, the method can measure an interference power and a path gain between an intended receiver and transmitter. Based upon the past performance of the network, a future interference value may be predicted by using a prediction algorithm. Furthermore, based upon the prior accuracy of the interference prediction, the method can also estimate an error margin for the interference prediction. Finally, a transmission power for the transmitter can be calculated using the predicted interference power, the estimated error margin for the predicted interference power, the path gain, and the target SINR.
|
1. A method for power control in a wireless network, comprising:
measuring an interference power value at an intended receiver for a first time slot; predicting a second interference power value at the intended receiver for a second time slot using the measured interference power value; estimating an error margin for the predicted second interference power value; and selecting a transmission power for the second time slot based on the predicted second interference power value and the error margin.
12. Method for power control in a wireless network using a kalman filter, comprising:
measuring an interference power value at a receiver for a time slot; inputting the measured interference power value to a kalman filter to predict a second interference power value at the receiver for a second time slot; estimating an error margin for the predicted second interference power value; and selecting a transmission power for the second time slot in order to meet a target signal to interference and noise ratio (SINR).
16. A wireless packet-switched communication system with power control, comprising:
at least one cell comprising; a base station having at least a transponder and an antenna; at least one mobile terminal including at least a transponder and an antenna; an electronic device for measuring an interference power value at an intended receiver for a time slot; a central processing unit (CPU) adapted to perform the steps of: predicting a second interference power value for a second time slot; estimating an error margin for the predicted second interference power value; and selecting a transmission power for the second time slot based at least the second interference power value and the error margin. 2. The method according to
determining a probability distribution of error between the predicted second interference power value and an actual second interference power value; and estimating the error margin based on a desired probability and the probability distribution of error.
3. The method according to
4. The method according to
5. The method according to
6. The method according to
8. The method according to
11. The method according to
13. The method according to
determining a probability distribution of error between the predicted second interference power value and an actual second interference power value; and estimating the error margin based on a desired probability and the probability distribution of error.
14. The method according to
15. The method according to
17. The method according to
determining a probability distribution of error between the predicted second interference power value and an actual second interference power value; and estimating the error margin based on a desired probability and the probability distribution of error.
18. The wireless communication system according to
19. The wireless communication system of
20. The wireless communication system of
21. The wireless communication system of
22. The wireless communication system according to
23. The wireless communication system according to
|
1. Field of Invention
The present invention relates to a method and system for power control by interference prediction with error margin for wireless Internet protocol (IP) networks.
2. Description of Related Art
The future generations of wireless networks must accommodate a growing demand for data packet services. High-speed packet services are necessary for wireless data packet communications, such as Internet protocol (IP), which can provide efficient access to remote networks and servers for telecommuters and to facilitate wireless multimedia services such as voice, audio, still-image and video.
Currently, cellular systems employ frequency reuse techniques whereby multiple cells in a network, known as co-channel cells, use the same set of frequencies. The frequency reuse factor of a cellular system is given by the variable N, where N is the cluster size which describes the number of cells which collectively use the complete set of available frequencies. The cluster size N should be chosen according to the amount of interference a mobile or base station can tolerate while maintaining a sufficient quality of communications. The total capacity of a cellular system is inversely proportional to the frequency reuse factor. Thus, decreasing the frequency reuse factor (i.e., the cluster size N) is essential for improving the capacity of cellular networks.
A major limiting factor in the performance of cellular wireless systems is interference. In particular, while frequency reuse improves capacity, it produces co-channel interference. Co-channel interference cannot be corrected by increasing the transmission power of the transmitter because increasing the transmission power raises the interference in neighboring co-channel cells. To reduce the co-channel interference, the co-channel cells must be physically separated by a minimum distance to provide sufficient isolation.
In order to improve the performance of time-division-multiple-access (TDMA) wireless networks and ensure that each base station and mobile terminal transmits the smallest power necessary to maintain a good quality radio link, power control within a network has become essential. Power control not only helps prolong battery life for the mobile units, but also can dramatically enhance the signal-to-interference-plus-noise ratio (SINR) in the system, and thus its error performance and capacity. Accordingly, dynamic transmission power control has been widely studied and practiced to combat and manage interference in cellular radio networks.
Known power control techniques for wireless networks can be categorized as either signal-based and signal-to-interference-ratio (SIR) based. In signal-based power control algorithms, the transmission power is adjusted based upon a received signal strength, which in turn depends upon the path loss, shadowing and fading of the radio link between the transmitter and the receiver. In contrast, SIR-based power control adjusts the power according to the ratio of the power level of the signal to the power level of the co-channel interference (possibly including noise). Studies have shown that SIR-based power control out performs signal-based power control, although the former involves a more complex implementation.
A drawback to both of these power control techniques is that they are applicable mainly to circuits switched connections having a relatively long holding time. Accordingly, these methods utilize iterative algorithms that require the re-adjustment of transmission power over the entire duration of a circuit switched connection and implicitly or explicitly, assume a relatively long call duration. However, the nature of the data traffic and packet-switched networks is bursty, which is fundamentally different from that of circuit-switched networks. For example, in TDMA packet-switched networks, time is divided into slots where the slot size is appropriately chosen to support the applications while controlling the protocol overhead to achieve efficient bandwidth usage. Typically, each data message is divided into a number of packets, each of which can be transmitted in one time slot. As in typical IP wireless networks, the message length (in terms of number of the number of packets) varies randomly from message to message.
Due to the bursty nature of the traffic and irregular transmission schedule inherent in packet-switched data networks, the traditional power control techniques, such as the above-described existing signal-based and SIR-based techniques, do not perform well. The above-described iterative power control methods for circuit switched networks are inefficient for packet-switched wireless network. Accordingly, new techniques have been developed to accommodate such bursting packet-switched network traffic. As described in co-pending U.S. patent application Ser. No. 09/273,125 filed on Mar. 19, 1999, one such system uses a Kalman filter to predict interference power and adjust a transmission power to achieve a target SINR performance.
Such a method relies on the fact that typical wireless networks allow multiple contiguous time slots to be used by a base station or mobile terminal for transmitting a message, and therefore a temporal correlation exists of the interference power between successive time slots. The temporal correlation allows the use of predictive methods, such as Kalman filters, to estimate the interference power in subsequent time slots. Accordingly, a signal path gain parameter and a prediction of the interference power for a future time slot can be used to calculate the power level for the future time slots in order to met a target SINR. However, the interference power prediction can become very inaccurate when each message consists of very few packets, such as where one packet is transmitted in one time slot. In addition, the performance gained by the method reduces when delay is incurred in interference measurements and in the forwarding of power control information from receivers to transmitters. Both of the situations of short messages and control delay are expected in certain wireless IP networks.
Accordingly, there is a significant need for a more efficient power control method for wireless networks.
The present invention provides a method and system for providing power control in a wireless packet switched network using interference prediction including an error margin. In particular, the method can measure an interference power and a path gain between an intended receiver and transmitter. Based upon the past performance of the network, a future interference value may be predicted by using a prediction algorithm, such as a Kalman filter. Furthermore, based upon the prior accuracy of the interference prediction algorithm, the method can also estimate an error margin for the predicted interference values. Finally, a transmission power for the transmitter can be calculated using the predicted interference power, the estimated error margin for the predicted interference power, the path gain, and the target SINR. Since the effects of short message and control delay have been reflected by the error margin, the enhanced power control method with such an error margin provides accurate interference power prediction, and thus yields a performance gain.
The invention is described in detail with regards to the following Figures, in which like elements are referred to with like numerals, and in which:
For the purposes of this application, a number of environmental and system conditions can be assumed. In particular, the uplink channel 137 and the downlink channel 135 are each subject to attenuation due to path gain (effectively attenuation) between the base station 105 and the mobile terminals 130. Effectively, the path gain is the sum of the path loss and the shadow fading for the radio link.
Furthermore, a medium-access control (MAC) protocol is used within the cell 107, which allows at most one mobile terminal 130 in each cell 107 to transmit at a time. That is, no data contention occurs within the same cell 107. Therefore, only one mobile terminal 130 communicates with the base station 105 in a given time slot. Due to the large volume of data involved, the base station 105 typically can not exchange control and scheduling information with another base station 105 operating in a different cell 107. Finally, the interference power for a particular time slot can be measured at the base station 105 and mobile terminals 130 but may include noise and errors.
According to one embodiment of the present invention, the interference power can be measured at an intended receiver, and then used as an input to a prediction algorithm to calculate a predicted interference. The predicted interference, along with an error margin calculated using an error estimating algorithm is used to set the power level for a transmitter. In particular, according to one embodiment of the present invention, to perform power control for the uplink channel 137 (i.e., from the mobile terminal 130 to the base station 105), the intended receiver, the base station 105, measures the interference power for a time slot. The controller 110 is adapted to estimate the interference level for a future time slot along with the estimated error margin of that interference and then calculate a power transmission level for the future time slot in order to meet a target signal-interference-noise-ratio (SINR). Upon determination of the power level for the future time slot, the base station 105 can instruct the mobile terminal 130 to transmit at the calculated power level, using the downlink channel 135.
According to one embodiment of the present invention, in order to perform downlink power control (i.e., from the base station 105 to the mobile terminal 130), the intended receiver, the mobile terminal 130, measures the interference power for a time slot. The mobile terminal 130 then transmits the measured interference power to the base station, which then runs a prediction algorithm along with the estimated error margin algorithm to calculate the power level for its own transmission at a future time slot. However, in an alternative embodiment, the mobile terminal 130 runs the prediction algorithm and estimated error margin algorithm itself and then transmits the calculated power level to the base station 105 via uplink channel 137.
In step 202, the process begins at the beginning of time slot n, the algorithm is initiated for the mobile terminal 130 scheduled to transmit in time slot n+1. In step 204, the current interference power Zn at the base station 105 (the intended receiver) is measured. Typically, the base station 105 would be equipped with an electronic device for measuring the current interference power. Methods for the measurement of interference power in wireless networks are well known. In general, the interference power is equal to the difference between the total power received and the power of the desired signal, where the power of the desired signal can be measured by filtering based upon a set of training symbols for the signal.
In step 206, the interference power for the time slot ĩn+1 (in linear power units) at the intended receiver, the base station 105, is predicted, where the mobile terminal 130 is scheduled to transmit in time slot n+1. The prediction can be implemented at the CPU 110 at the base station 105, which is adapted to run a prediction algorithm. According to a preferred embodiment, the prediction algorithm employed is a Kalman filter as described in detail below with reference to FIG. 4.
In step 208 the process estimates an error margin for {tilde over (e)}n+1 the interference prediction Ĩn+1 for time slot n+1. The error margin {tilde over (e)}n+1 can be calculated based on the accuracy of the predicted interference power Ĩn+1. For example, an interference prediction error may be calculated for a time slot as the difference between the predicted interference power and the measured interference power. Over time, successive measurements of the interference prediction error can be aggregated into a prediction error distribution.
For instance, let the actual prediction error for time slot n be:
where In and Ĩn are the measured and predicted interference power in dBm for time slot n, respectively. Let there be M possible intervals of prediction error and the range of the jth interval be from aj to aj+1. For each time slot n and each j=1 to M, compute the following:
Where α is a properly chosen parameter and we set Poj=1 for all j=1 to M initially.
By way of example, to achieve a probability of 0.9 that the actual error is less than the predicted interference determined in steps 206, the error margin {tilde over (e)}n+1 for the plot 302 is aK.
In step 210, a path gain parameter gn+1 between the mobile terminal 130 and the base station 105 is measured. The methods for determination of the path gain gn+1 between a mobile terminal 130 and a base station 105 in a wireless network are well known. In an alternative embodiment, the path gain is not measured for every time slot, but rather is measured once at the beginning of a message transmission and is used for the duration of the message transmission (i.e., for all packets comprising a message).
In step 212, the transmission power for the mobile terminal 130 scheduled to transmit in time slot n+1 is calculated using the equation:
where β* is a target SINR, gn+1 is the estimated path gain parameter, and Ĩn+1 is the predicted interference power for the time slot n+1 and {tilde over (ω)}n+1 is the linear equivalent of {tilde over (e)}n+1 defined above. The desired result of the relationship in equation (1) is to choose the minimum power necessary to achieve the target SINR, and therefore minimize any interference with others without degrading the local link quality. According to one embodiment of the present invention, different SINR targets (β*) can be applied in equation (1) for different mobile terminals 130, depending on the path gain (gn+1) to the particular base station 105 and the application requirements. For example, for a poor radio link with large path attenuation and unfavorable shadowing, the link can adapt to the poor quality by reducing its data rate. Thus, a lower SINR target (β*) may be used in equation (1) to support decreased data rate for the mobile terminal 130.
In step 214, the base station 105 instructs the mobile station 130 to transmit at the power level Pn+1 for the time slot n+1 via the down link channel 135.
The embodiment described above describes power control for the uplink 137 channel (i.e., from the mobile terminal 130 to the base station 105). However, the present invention may also be applied for power control to the downlink 135 (i.e., between the base station 105 and the mobile station 130) with departing from the spirit and the scope of the present invention.
where Fn, the process noise, represents the fluctuation of interference power for slot n as terminals may start new transmissions and/or adjust their transmission power in the time slot. Zn is the measured interference power in time slot n as described by the following relationship:
where Δnis referred to as the measurement noise.
The algorithm for the prediction of the interference power for the succeeding time slot is initiated in step 405. The measured interference power at time slot n, Zn (see
In step 410a, the mean measurement value for the last W time slots is calculated using previously stored measurement values Zn-W+1 through the current measurement value for time slot n, Zn as follows:
In step 410b, the variance of the process noise, Qn is estimated by calculating the variance of the measurement values for the last W time slots as follows:
This estimate of the variance of the process noise, Qn provides an estimate of the variance of the sum of the process noise and measurement noise because interference power measurements Zn include the fluctuation of both interference and measurement errors. However, because the standard deviation of the interference power can reach as much as tens of decibels, which greatly exceeds typical measurement errors, estimating Qn in this manner yields a relatively accurate variance for the process noise Fn.
In step 410c, the variance of the measurement noise, Rn is calculated using the relationship:
where η is a proportionality constant between 0 and 1. The choice of Rn according to equation (6) is reasonable because the measurement noise (error) is likely to be proportional to, but smaller than, the fluctuations of the interference power.
In step 420, the Kalman gain is computed using the following relationship:
where {tilde over (P)}n is the priori estimate of the measurement error variance.
In step 430, the Kalman gain, Kn, is used to obtain an a posteriori estimate of the interference noise using the measurement for the current time slot Zn as follows:
In step 440, the a posteriori estimate error variance is computed as follows:
In step 450, the estimate error variance is predicted for time slot n+1 as follows:
Finally, in step 460, the interference power for time slot, n+1, is predicted using the relationship:
Ĩn+1=În (11)
Results for the optimal power control characteristic curve, shown by the solid line in
Simulations were run using different values for the average message length, L, and the control delay, D. In particular,
As shown in
While this invention has been described in conjunction with the specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, preferred embodiments of the invention as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the spirit and scope of the invention.
Patent | Priority | Assignee | Title |
10278196, | Nov 25 2014 | Samsung Electronics Co., Ltd. | Method for data scheduling and power control and electronic device thereof |
10542500, | Mar 19 2007 | Apple Inc. | Resource allocation in a communication system |
10681711, | Nov 25 2014 | Samsung Electronics Co., Ltd | Method for data scheduling and power control and electronic device thereof |
10701640, | Mar 19 2007 | Apple Inc. | Resource allocation in a communication system |
12177875, | Mar 08 2022 | Qualcomm Incorporated | Soft interference prediction in a wireless communications system |
6728299, | Jun 28 2002 | Nokia Technologies Oy | Transmitter gain control for CDMA signals |
6778955, | Nov 09 1998 | VIVOSONIC INC | System and method for processing low signal-to-noise ratio signals |
6904021, | Mar 15 2002 | ARRIS ENTERPRISES LLC | System and method for providing adaptive control of transmit power and data rate in an ad-hoc communication network |
6987738, | Jan 12 2001 | Google Technology Holdings LLC | Method for packet scheduling and radio resource allocation in a wireless communication system |
6988212, | Sep 29 2000 | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | Method and system for adaptive power control in a networking system |
7124193, | Aug 24 2000 | HANGER SOLUTIONS, LLC | Method of using link adaptation and power control for streaming services in wireless networks |
7286983, | Nov 09 1998 | Vivosonic Inc. | System and method for processing low signal-to-noise ratio signals |
7389133, | Sep 23 2003 | Roche Diabetes Care, Inc | Method and device for continuous monitoring of the concentration of an analyte |
7453861, | Aug 02 2002 | AT&T Corp | System and method for estimating interference in a packet-based wireless network |
7454224, | Dec 22 2003 | Nokia Technologies Oy | Method for improving the performances of a mobile radiocommunication system using a power control algorithm |
7454512, | Aug 24 2000 | HANGER SOLUTIONS, LLC | Method of using link adaptation and power control for streaming services in wireless networks |
7536626, | Jun 18 2004 | Qualcomm, INC; Qualcomm Incorporated | Power control using erasure techniques |
7594151, | Jun 18 2004 | Qualcomm, Incorporated | Reverse link power control in an orthogonal system |
7656846, | Nov 18 2002 | GE Fanuc Automation North America, Inc. | PLC based wireless communications |
7688724, | Dec 23 2005 | ARLINGTON TECHNOLOGIES, LLC | Call admission control for mobility-capable telecommunications terminals |
7711033, | Apr 14 2005 | Telefonaktiebolaget LM Ericsson (publ) | SIR prediction method and apparatus |
7742444, | Mar 15 2005 | QUALCOMM INCORPORATED A DELAWARE CORPORATION | Multiple other sector information combining for power control in a wireless communication system |
7852963, | Mar 05 2004 | RPX Corporation | Method and system for predicting signal power to interference metric |
7873362, | Sep 24 2004 | CLUSTER, LLC; Optis Wireless Technology, LLC | Method for dimensioning or evaluating a radio network |
7962826, | Jul 20 2004 | Qualcomm Incorporated | Reverse link power control in an orthogonal system |
8004979, | Dec 23 2005 | ARLINGTON TECHNOLOGIES, LLC | Call admission control for mobility-capable telecommunications terminals |
8023987, | Sep 28 2005 | Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung E V | Signaling method for decentralized allocation of online transmission power in a wireless network |
8059553, | Aug 21 2007 | FiMax Technology Limited | Adaptive interference control |
8081560, | Aug 31 2007 | RPX Corporation | Method and apparatus for self-tuning precoder |
8195097, | Sep 08 2006 | Qualcomm Incorporated | Serving sector interference broadcast and corresponding RL traffic power control |
8199661, | Oct 27 2006 | Qualcomm Incorporated | Method and apparatus for processing supplemental and non supplemental assignments |
8218479, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for processing a multi-code word assignment in wireless communication systems |
8238289, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for requesting selected interlace mode in wireless communication systems |
8248950, | Oct 27 2005 | Qualcomm Incorporated | Method of transmitting and receiving a redirect message in a wireless communication system |
8265066, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for reducing power consumption in wireless communication systems |
8289897, | Oct 27 2005 | Qualcomm, Incorporated | Method and apparatus for processing open state in wireless communication system |
8289908, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for processing simultaneous assignment in wireless communication systems |
8326330, | Oct 27 2005 | Qualcomm, Incorporated | Method and apparatus for updating configuration attributes using FastRepage attribute in wireless communication systems |
8331285, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus of establishing access channel in wireless communication systems |
8442572, | Sep 08 2006 | Qualcomm Incorporated | Method and apparatus for adjustments for delta-based power control in wireless communication systems |
8452316, | Jun 18 2004 | Qualcomm Incorporated | Power control for a wireless communication system utilizing orthogonal multiplexing |
8457042, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for transmitting and receiving a sectorparameters message in an active state in wireless communication system |
8457092, | Jun 16 2005 | Qualcomm Incorporated | Quick paging channel with reduced probability of missed page |
8477808, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus of assigning in wireless communication systems |
8478202, | Jun 18 2004 | Qualcomm Incorporated | Power control for a wireless communication system utilizing orthogonal multiplexing |
8488459, | Mar 04 2005 | Qualcomm Incorporated | Power control and quality of service (QoS) implementation in a communication system |
8488487, | Sep 08 2006 | Qualcomm Incorporated | Method and apparatus for fast other sector interference (OSI) adjustment |
8516314, | Jun 18 2004 | Qualcomm Incorporated | Robust erasure detection and erasure-rate-based closed loop power control |
8520628, | Oct 27 2005 | Qualcomm, Incorporated | Method and apparatus for monitoring other channel interference in wireless communication system |
8521213, | Sep 08 2006 | Qualcomm Incorporated | Serving sector interference broadcast and corresponding RL traffic power control |
8539111, | Dec 30 1999 | AVAYA Inc | Port switch |
8543152, | Jun 18 2004 | Qualcomm Incorporated | Power control for a wireless communication system utilizing orthogonal multiplexing |
8599712, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for setting reverse link CQI reporting modes in wireless communication system |
8665742, | Aug 24 2000 | HANGER SOLUTIONS, LLC | Method of using link adaptation and power control for streaming services in wireless networks |
8670777, | Sep 08 2006 | Qualcomm Incorporated | Method and apparatus for fast other sector interference (OSI) adjustment |
8675549, | Oct 27 2005 | Qualcomm, Incorporated | Method of serving sector maintenance in a wireless communication systems |
8676964, | Jul 31 2008 | RIVERBED TECHNOLOGY LLC | Detecting outliers in network traffic time series |
8730885, | Feb 07 2011 | Alcatel Lucent | Method for improved robust header compression with low signal energy |
8744444, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for transmitting a pilot report (PilotReport) message in wireless communication systems |
8750908, | Jun 16 2005 | Qualcomm Incorporated | Quick paging channel with reduced probability of missed page |
8761080, | Mar 15 2006 | Qualcomm Incorporated | Multiple other sector information combining for power control in a wireless communication system |
8848574, | Mar 15 2005 | Qualcomm Incorporated | Interference control in a wireless communication system |
8849210, | Mar 15 2005 | Qualcomm Incorporated | Interference control in a wireless communication system |
8849334, | Apr 27 2006 | TELEFONAKTIEBOLAGET LM ERICSSON PUBL | Power control in a wireless system having multiple interfering communication resources |
8879425, | Mar 15 2005 | Qualcomm Incorporated | Interference control in a wireless communication system |
8923211, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus of processing an access grant block in wireless communication systems |
8929908, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for estimating reverse link loading in a wireless communication system |
8942639, | Mar 15 2005 | Qualcomm Incorporated | Interference control in a wireless communication system |
8971222, | Oct 27 2005 | QUALCOMM INCORPORATED, A DELAWARE CORPORATION | Method and apparatus for decrementing assignments in wireless communication systems |
9055552, | Jun 16 2005 | Qualcomm Incorporated | Quick paging channel with reduced probability of missed page |
9125078, | Oct 27 2005 | Qualcomm Incorporated | Method and apparatus for setting reverse link CQI reporting modes in wireless communication system |
9295003, | Mar 19 2007 | MORGAN STANLEY SENIOR FUNDING, INC | Resource allocation in a communication system |
9848431, | Nov 25 2014 | Samsung Electronics Co., Ltd | Method for data scheduling and power control and electronic device thereof |
Patent | Priority | Assignee | Title |
6097947, | Apr 22 1997 | NEC Corporation | Method for detecting failure mobile station in cellular mobile communication network through transmission power control |
6101176, | Jul 24 1996 | Nokia Technologies Oy | Method and apparatus for operating an indoor CDMA telecommunications system |
6122260, | Dec 16 1996 | BEIJING XINWEI TELECOM TECHNOLOGY CO , LTD | Smart antenna CDMA wireless communication system |
6363252, | Sep 17 1997 | Nokia Mobile Phones Ltd. | Advanced method for executing handover |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Dec 15 1999 | AT&T Corp. | (assignment on the face of the patent) | / | |||
May 10 2000 | LEUNG, KIN K | AT&T Corp | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 010819 | /0140 | |
Mar 30 2012 | AT&T INTELLECTUAL PROPERTY II, L P | Chanyu Holdings, LLC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 028199 | /0415 |
Date | Maintenance Fee Events |
Jun 22 2006 | M1551: Payment of Maintenance Fee, 4th Year, Large Entity. |
Sep 20 2010 | REM: Maintenance Fee Reminder Mailed. |
Feb 11 2011 | EXP: Patent Expired for Failure to Pay Maintenance Fees. |
Date | Maintenance Schedule |
Feb 11 2006 | 4 years fee payment window open |
Aug 11 2006 | 6 months grace period start (w surcharge) |
Feb 11 2007 | patent expiry (for year 4) |
Feb 11 2009 | 2 years to revive unintentionally abandoned end. (for year 4) |
Feb 11 2010 | 8 years fee payment window open |
Aug 11 2010 | 6 months grace period start (w surcharge) |
Feb 11 2011 | patent expiry (for year 8) |
Feb 11 2013 | 2 years to revive unintentionally abandoned end. (for year 8) |
Feb 11 2014 | 12 years fee payment window open |
Aug 11 2014 | 6 months grace period start (w surcharge) |
Feb 11 2015 | patent expiry (for year 12) |
Feb 11 2017 | 2 years to revive unintentionally abandoned end. (for year 12) |